考虑余高的焊缝内部缺陷全聚焦超声成像检测

Ultrasonic Imaging Testing of Defects in Welds Having Caps with Total Focusing Method

针对存在余高对接焊缝检测空间受限、垂直入射声能发散,导致焊缝内部缺陷检测困难问题,开展全聚焦(Total Focusing Method,TFM)超声成像检测研究。仿真建立曲率半径6 mm、余高高度2.4 mm的碳钢对接焊缝模型,并设置深度20 mm的?2横通孔。利用TFM对焊缝模型表面轮廓位置进行提取,进而实现横通孔检出,成像质量优于B扫描、合成孔径聚焦技术和表面契合超声法,缺陷幅值和信噪比分别可达-14.96 dB和17.82 dB。试验得到的横通孔幅值和信噪比分别为-21.39 dB和7.51 dB,验证了方法可行性。在曲率半径18 mm、余高高度3.6 mm的对接焊缝内部设置5~30 mm不同深度?2横通孔,仿真检测结果显示,受超声衰减和参与成像信号数量影响,横通孔回波幅值随孔深增加呈现先降低、后升高再降低的现象。

Ultrasonic imaging testing was carried out with total focusing method(TFM)to solve the problem of defect detection in butt welds where detective space was limited and vertical incident sound energy was diverged due to the existences of caps.A carbon steel butt weld model was created with 6 mm of curvature radius and 2.4 mm of cap height,and a?2 side drilled hole(SDH)in 20 mm depth was set in the weld.Additionally,TFM was employed to realize the contour position extraction of weld surface for detecting SDH.The imaging quality was better than that of B-scan,synthetic aperture focusing technology and surface adaptive ultrasound method,whose defect amplitude and signal-to-noise ratio were-14.96 dB and 17.82 dB,respectively.Besides,the amplitude and signal-to-noise ratio of the hole obtained by experiments were-21.39 dB and 7.51 dB,respectively,verifying the feasibility of this method.In the butt welds with an 18 mm curvature radius and a 3.6 mm cap height,a series of?2 SDHs were set at 5-30 mm depth.The simulation results exhibited that the echo amplitudes of SDH firstly reduced,then increased and finally decreased with the increase of the hole depth,which were affected by the attenuation and the number of imaging signals.